Lipoteichoic acid, a major amphiphilic molecule of Gram positive bacteria, occurs in membranous organelles known as mesosomes. The purpose of this work has been to determine the functional role of lipoteichoic acid (LTA) and mesosomes in the growth of the staphylococcal and streptococcal cells. Present studies have been directed at determination of some of the unique properties of LTA, namely, the density, degree of aggregation, and affinity to various surfaces. We have demonstrated that LTA exists in several different interconvertable aggregation states. Recently, we separated staphylococcal mesosomes into two distinct density types which were further fractionated by osmotic lysis and centrifugation.